Structural design verifications, structural analysis of tunnels - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 127

The results of the calculation show that greater curvatures of the cross-section were de-
termined for the steel fibre shotcrete than for mesh-reinforced shotcrete in every case.
Related to the overall structure, this means that higher angles of rotation can be reached
in cracked zones and thus higher moment redistribution can be achieved. In summary, a
tunnel lining of steel fibre shotcrete is thus capable of resisting more load.
Summary. Due to its properties of following bending deformation without fracture and
simultaneously resisting high normal forces, steel fibre shotcrete is generally suitable as a
material for tunnel linings. If the redistribution of bending moments due to crack forma-
tion and the increased activation of subgrade reaction are to be useful for calculations, the
required plastic rotation should be verified. The experimental investigations carried out at
the Ruhr-University, Bochum with eccentrically loaded steel fibre concrete beams show
how steel fibre concrete can be designed and the verification of rotation capability can be
performed for tunnel linings.
A qualitative comparison of mesh-reinforced shotcrete and outer tunnel linings of steel fi-
bre shotcrete shows that the latter has a more homogeneous internal structure, less defects
in the form of spraying shadows, a better bond between the individual layers of shotcrete
and the altogether higher load-bearing capacity and water permeability can be achieved.
The quantitative comparison of calculated M- k curves makes clear that the moment capac-
ity depends on the magnitude of the normal force. Steel fibre shotcrete can show a higher
moment capacity then mesh-reinforced shotcrete at higher load factors of normal force.
It has also been demonstrated that greater curvatures of the cross-section can be achieved
with steel fibre shotcrete. Related to the overall structure, this means that higher angles
of rotation can be reached in cracked zones and thus higher moment redistribution can be
achieved.